1. The Field of the Invention
This invention relates to an improvement in machines for band wrapping of articles.
2. Technical Background
Band wrapping of articles is widely practiced and involves assembling a group of individual articles on a support and then winding flexible sheet material obtained from a roll round the assembly so that it can be handled as a single entity. The assembly is generally of rectangular shape and comprises a number of rectangular articles or articles of other shapes which can nevertheless be arranged into a rectangular or other regular shaped assembly. The latter can be either single or double wrapped. In the former case, the assembly will have both its top and bottom covered and also one pair of opposing sides.
When single wrapping is employed, it is customary to allow the wrapping material covering opposing sides just to extend round the ends of the assembly so as to cover a small part of the otherwise unwrapped sides. In this way some additional containment of the assembly can be achieved. When the assembly is wrapped on all four sides, it is said to be double wrapped. During the unwinding of wrapping material from the roll the material tends to stretch and its width to diminish or "neck".
A considerable variety of fibrous and filmic sheet materials have been used for band wrapping although those that are employed most extensively are flexible sheets of different forms of synthetic plastics materials which have varying degrees of stretchability when subjected to tension.
A material which has been developed recently known as "one side cling stretch film" is of especial use for wrapping purposes. This material is highly stretchable synthetic plastics material which has mildly pressure sensitive adhesive qualities on one side and little or no such properties on the reverse side. Consequently, very satisfactory packages can be used with this material because overlapping bands of the surrounding articles cling to one another and thereby improve the integrity of the wrapping. At the same time, if two packages came into contact, they do not adhere to one another or to other surfaces, for example, the surfaces of mechanical handling conveyors.
One of the problems encountered in band wrapping with existing machines stems from the fact that the sizes of different assemblies to be wrapped can vary greatly. On the other hand, band wrapping has to be carried out in a precise way if satisfactory packages are to be obtained.
Consequently, in order to meet all likely requirements, either the supplier or the user of the wrapping material has to retain in stock a considerable number of rolls of material of different widths. This is both costly and inconvenient. The present invention provides a machine which is directed to overcoming this problem as well as making available other advantages.